i know there are lots of internet bought products to pass these but is there anything i can buy in a store ?
hair follicle? I dont know of a single product on the internet or store that would help you pass one of those. all the 'pass a drug test' products available on the net are for piss tests, which is very cheap compared to hair follicle. If someone is testing your hairs for drugs, you either did something very bad, or are going for a really good job. either way your fucked.
I thought there were shampoos you can find in a head shop to get rid of traces for a day or few hours at least. Don't know if they work though.
that way id get caught anyways, this would be the only reason id ever shave my head, it would be known that i did something i didnt want to be found >.<